Magnetoresistance effect element

ABSTRACT

A magnetoresistance effect element comprises the multilayer formed by alternately stacking magnetic and nonmagnetic layers. The magnetic layers containing at least two magnetic elements selected from a group of magnetic elements consisting of Fe, Co and Ni. Any two magnetic layers adjacent to each other with one of the nonmagnetic layer interposed therebetween are antiferro-magnetically coupled under a condition where a magnetic field is not substantially applied thereto.

This application is a continuation of application Ser. No. 07/858,413,filed on Mar. 27, 1992, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a magnetoresistance effect element formed byusing multilayer of ultra-thin layers or a so-called artificial latticefilm.

2. Description of the Related Art

The magnetoresistance effect is an effect of varied resistance of anobject caused by the variation in the intensity of the magnetic fieldapplied to it. Magnetoresistance effect elements that utilize thiseffect find a variety of applications including those for magnetic fieldsensors and magnetic heads because of the high sensitivity to magneticfields and the ability to produce a relatively large output of suchelements. While Permalloy thin film is wide used for magnetoresistanceeffect elements, the magnetoresistance ratio of a Permalloy foil (ΔR/Rs:where ΔR is the electric resistance change between zero magnetic fieldand saturated magnetic field; Rs is saturation resistivity) is as low as2 or 3% and, therefore, does show a satisfactory sensitivity to changesin the magnetic field required for a magnetoresistance effect element.

Meanwhile, as new magnetoresistance effect element, multilayer formed byalternately stacking magnetic and nonmagnetic layers having a thicknessof several to tens of Angstroms or so-called artificial lattice filmshave been attracting attention. Known types of artificial lattice filminclude (Fe/Cr)_(n) (Phys. Rev. Lett. vol. 61(21) (1988)2472), (Permalloy/Cu/Co/Cu)_(n) (J. Phys. SOC. Jap. vol. 59(9) (1990) 3061) and(Co/Cu)_(n) (J. Mag. Mag. Mat. 94, (1991)L1; Phys. Rev. Lett.66(1991)2152).

While an artificial lattice film can present a dramatically enhancedmagnetoresistance effect when compared with a Permalloy thin film,artificial lattice films having a remarkable magnetoresistance effectcan be currently produced only by a film forming apparatus capable ofcarrying out a supervacuum processing, which uses a supervacuumtechnique such as the ultra-high vacuum evaporation (UHV) method or themolecular beam epitaxy (MBE) method. Artificial lattice films preparedin an ordinary film forming apparatus do not unfortunately show asatisfactory magnetoresistance effect.

SUMMARY OF THE INVENTION

In view of these circumstances, it is therefore an object of the presentinvention to provide a magnetoresistance effect element which has largemagnetoresistance ratio and which can be applied to a practical use evenwhen the element is produced in an ordinary thin film forming apparatus.

According to the invention, the above object is achieved by providing amagnetoresistance effect element comprising multilayer formed bystacking magnetic and nonmagnetic layers, said magnetic layerscontaining at least two magnetic elements selected from Fe, Co and Ni,any two magnetic layers adjacent to each other with one of saidnonmagnetic layer interposed therebetween being antiferromagneticallycoupled under a condition where a magnetic field is not substantiallyapplied thereto.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 a schematic sectional view of a magnetoresistance effect elementaccording to an embodiment of the present invention.

FIG. 2 is a graph illustrating the relationship between the thickness ofa nonmagnetic layer of magnetic multilayer and magnetoresistance ratioof the element.

FIG. 3 is a graph illustrating the relationship between the thickness ofa nonmagnetic layer of magnetic multilayer and saturated field of theelement.

FIG. 4 is a graph showing the magnetoresistance ratio of Example 1.

FIG. 5 is a graph showing the magnetoresistance curve of Example 2.

FIG. 6 is a graph showing the magnetoresistance curve of Example 3.

FIG. 7 is a graph showing the magnetoresistance curve of Example 4.

FIG. 8 is a graph showing the magnetoresistance curve of Example 5.

FIG. 9 is a graph showing the magnetoresistance curve of Example 6.

FIG. 10 is a graph showing the magnetoresistance curve of ComparisonExample 1.

FIG. 11 is a graph showing the magnetoresistance curve of ComparisonExample 2.

FIG. 12 is a graph showing torque curve of Example 12.

FIG. 13 is a graph showing the magnetoresistance curve of Example 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As a result of intensive research efforts of the inventors of thepresent invention to develop artificial lattice films that show a largemagnetoresistive effect, they came to find that the magnetoresistanceeffect of a (Co/Cu)_(n) type artificial lattice film is remarkablyenhanced when the Co is partly substituted by Fe. They also found thatthe effect can be obtained when the magnetic layers contain at least twoof Fe, Co and Ni and the effect is particularly large when any twoneighboring magnetic layers are antiferromagnetically coupled under acondition where a magnetic field is not substantially applied thereto.The present invention is achieved based on the findings of the presentinventors.

The present invention will now be explained in detail.

A magnetoresistance effect element according to the present inventioncomprises a multilayer prepared by alternately stacking magnetic andnonmagnetic layers and typically has a configuration as shown in FIG. 1,where a total of n identical combinations of a nonmagnetic layer 2 and amagnetic layer 3 are vertically stacked on a substrate 1. Here, thelowest layer may be a non-magnetic one or a magnetic one. A buffer layermade of a soft magnetic material may be interposed between the substrate1 and the multilayer.

The magnetic layers contain at least two of Fe, Co and Ni as maincomponents. In other words, they are made of an Fe--Co alloy, an Fe--Nialloy, an Fe--Ni--Co alloy or Co--Ni alloy, although they may containother elements. Of the above alloys, an Fe--Co alloy is preferable inorder to obtain a large magnetoresistance change. For Fe--Ni alloy, theuse of a Permalloy represented by formula Ni_(1-x) Fe_(x) (where0<x≦0.64) is preferable in order to obtain a relatively largemagnetoresistance change with low saturation field. The magneticpermeability and the magnetoresistance ratio of the Permalloy can beimproved by substituting the Fe contained there with another element(e.g., Mo, Mn, Cu, Cr). The magnetic layers preferably have in-planeuniaxial magnetic anisotropy.

It is preferable that any neighboring ones of the magnetic layers areantiferromagnetically coupled under a condition where a magnetic fieldis not substantially applied thereto. Here, "antiferromagneticallycoupled" means that the layers are coupled in such a manner that themagnetic moments of any two neighboring magnetic layers are inverselydirected. Such an arrangement coupling can increase themagnetoresistance ratio. On the other hand, the force with whichneighboring layers are antiferromagnetically coupled is preferably assmall as possible because the smaller the antiferromagnetically couplingforce is, the smaller the saturation field (H_(S)) is, and therefore themore advantageous for applications including those for magnetic heads.It is advantageous that the saturated magnetic field H_(S) of an elementaccording to the invention is small in view of increasing themagnetoresistance ratio (ΔR/R) by using small magnetic field.

Any material may be used for the nonmagnetic layers of an elementaccording to the present invention as far as the material allows theelement to have the magnetoresistance effect. Preferable materials thatcan be used for nonmagnetic layers for the purpose of the presentinvention include Cur Cr, Au, Ag and Ru, which may be used as a singlematerial or in the form of an alloy containing any of them. When anonmagnetic layer made of Cu--Au alloy, the antiferromagnetic couplingforce between two neighboring layers can be reduced.

While magnetic metal layers and nonmagnetic layers may be combined inmany different ways, the following combinations are recommendable fromthe viewpoint of obtaining large magnetoresistance effect.

1) The magnetic layers are made of an alloy represented by formulaFe_(1-x) Co_(x) (where 0.5≦x<1, preferably 0.5≦x≦0.999) and thenonmagnetic layers are made of Cu.

2) The magnetic layers are made of an alloy represented by formulaFe_(1-x) Co_(x) (where 0<x≦0.8, preferably 0<x≦0.5) and the nonmagneticlayers are made of Cr.

3) The magnetic layers are made of an alloy represented by formulaNi_(1-y) (Fe_(1-x) Cox)y, where 0≦x≦1 and 0<y<1, and the nonmagneticlayers are made of Cu.

4) The magnetic layers are made of an alloy represented by formulaNi_(1-y) (Fe_(1-x) Cox)_(y), where 0≦x≦0.9 and 0.7≦y<1, and thenonmagnetic layers are made of Cr.

If the magnetic layers contain an alloy represented by Fe₁×x Co_(x),then x may have a value of 0.5<x≦0.8. If the magnetic layers contain analloy represented by Ni_(1-y) (Fe_(1-x) Co_(x))_(y), then x may have avalue of 0.5≦x≦1.

In order to obtain a sufficiently large magnetoresistance ratio (ΔR/R),the thickness t_(M) (as expressed in terms of Angstrom or A) of amagnetic layer preferably falls within the range represented by 2A≦t_(M) ≦100 A, while the thickness t_(N) (as expressed in terms ofAngstrom or A) of a nonmagnetic layer preferably falls within the rangerepresented by 2 A≦t_(N) ≦100 A. More preferably, they fall within therange represented by 7 A ≦t_(M) ≦90 A and 9A ≦t_(N) ≦50 A respectively.

The relationship between the thickness of a nonmagnetic layer and themagnetoresistance ratio can be graphically expressed in a manner asshown in FIG. 2. Since the magnetoresistance ratio oscillatory changesas a function of the thickness t_(N) of the nonmagnetic layer, thethickness t_(N) is preferably found within the range represented aboveso as to show a large magnetoresistance ratio. On the other hand, as isshown in FIG. 3, the saturated magnetic field also cyclically changes asa function of the thickness of the nonmagnetic layer with the peakssubstantially agreeing with those of the magnetoresistance ratio.Therefore, it may be understood that the thickness of the nonmagneticlayer should be so determined that the magnetoresistance ratio and thesaturated magnetic field has a relationship optimal to the specificapplication of the element. FIGS. 2 and 3 illustrate the result of anexperiment conducted at room temperature, using multilayer comprisingsixteen magnetic layers made of Fe₀.1 Co₀.9 and having a thickness of 10A and a same number of nonmagnetic layers made of copper and havingdifferent thicknesses which are found within the above range.

The number of combined layers is preferably between 5 and several tens.While a larger number may be advantageous from the viewpoint ofmagnetoresistance ratio, the effect reaches a saturated level and willnot be improved any further if the number is large. Therefore, it ispreferable that the number of combined layers is defined within a rangewhere the magnetoresistance effect does not get to a saturated level.

The material to be used for the substrate for a multilayer according tothe present invention does not need to be specifically defined.Materials that can be used for the substrate include SiO, MgO spinel,and Si.

The multilayer described above can be prepared by means of ordinary thinfilm forming techniques involving an initial vacuum level of 10⁻⁷ Torror less (or a pressure equal to 10⁻⁷ Torr or more) such as the RFmagnetron sputtering method, the ion beam sputtering (IBS) method andthe vacuum evaporation method as well as techniques involving asupervacuum condition such as the molecular beam epitaxy method and thesupervacuum sputtering method.

A magnetoresistance effect element utilizing a conventional artificiallattice film that comprises magnetic layers made of a single elementsuch as (Co/Cu)_(n) and (Fe/Cr)_(n) shows a magnetoresistance ratiobetween 20 and 50% if it is prepared by a film forming apparatusutilizing a supervacuum method such as UHV. However, themagnetoresistance radio of the element falls to an unsatisfactory levelof several percent if it is prepared by an apparatus involving anordinary initial vacuum level. To the contrary, a magnetoresistanceeffect element according to the present invention can be prepared by anordinary film forming apparatus to show a sufficient magnetoresistanceratio for practical use.

It should be noted that neither the magnetic nor the nonmagnetic layersof the multilayer of a device according to the invention need to have anidentical chemical composition and an identical thickness.

Now, the present invention will be described by way of examples.

EXAMPLE 1

In this example, magnetic layers were made of a Fe₀.1 Co₀.9 alloy andnonmagnetic layers were made of Cu. The ion beam sputtering method wasused to prepare multilayer.

A quartz substrate was placed in a chamber and the inside of the chamberwas evacuated to 5×10⁻⁷ Torr. Then, Ar gas was introduced into thechamber to raise the pressure to 1×10⁻⁴ Torr and a sputtering operationwas carried out, using an accelerating voltage of 500 V and a beamcurrent of 30 mA. Three different types of targets made of iron Fe₀.1Co₀.9 alloy, Cu were used. Firstly, an Fe target was sputtered to form abuffer layer having a thickness of 50 A on the quartz substrate.Subsequently, a Cu target and a Fe₀.1 Co₀.9 alloy target werealternately sputtered fifteen times to stack fifteen unit layers eachcomprising a nonmagnetic Cu layer having a thickness of 9 A and amagnetic Fe₀.1 Co₀.9 alloy layer having a thickness of 7 A, (the numberof the unit layer is 15), thereby forming the multilayer as shown inFIG. 1. The multilayer is referred to (Fe₀.1 Co₀.9 7 A/Cu9 A)₁₅.

While a buffer layer was formed in the above embodiment, the bufferlayer is not necessarily required for the purpose of the presentinvention.

Then, the magnetoresistance effect of the prepared multilayer wasmeasured by means of the conventional four points method, which iscommonly used in the field of the present invention. FIG. 4 illustratesthe result of the measurement. In FIG. 4, the transverse and verticalaxes respectively indicates the intensity of magnetic field and thenormalized electric resistance (R/R (H=0)), when the resistance of theelement is 1 under the condition of the magnetic field intensity of 0,so that the relationship between the magnetoresistance effect and theelectric resistance of the element is illustrated there. Themagnetoresistance ratio ΔR/R was determined from the graph to show themagnetoresistance effect of the element. It was 7.5%, or asatisfactorily large value. It was confirmed that the multilayer whichused a Fe₀.1 Co₀.9 alloy for the magnetic layers and Cu for thenonmagnetic layers was suitable for a magnetoresistance effect element.

EXAMPLE 2

In this example, magnetic layers were made of a Fe₀.25 Co₀.75 alloy thenonmagnetic layers were made of Cu. The ion beam sputtering method wasused to prepare multilayer.

Firstly, an Fe buffer layer having a thickness of 50 A was formed on aquartz substrate. Subsequently, Cu and Fe₀.25 Co₀.75 alloy targets werealternately sputtered fifteen times to stack fifteen unit layers eachcomprising nonmagnetic Cu layers having a thickness of 9 A and magneticFe₀.25 Co₀.75 alloy layers having a thickness of 7 A (the number of theunit layer is 15), thereby forming multilayer, as shown in FIG. 1. Acondition of film formation was identical with that of Example 1. Themultilayer is referred to (Fe₀.25 Co₀.75 7 A/Cu9 A)₁₅.

Then, the magnetoresistance effect of the prepared multilayer wasmeasured by means of the conventional four points method. FIG. 5, whichappears similar to FIG. 4, illustrates the result of the measurement.The magnetoresistance ratio ΔR/R was determined from the graph to showthe magnetoresistance effect of the element. It was 11.1%, or asatisfactorily large value. It was confirmed that the multilayer whichused a Fe₀.25 Co₀.75 alloy for the magnetic layers and Cu for thenonmagnetic layers was suitable for a magnetoresistance effect element.

EXAMPLE 3

In this example, magnetic layers were made of a Fe₀.1 Co₀.9 alloy andnonmagnetic layers were made of Cu. The ion beam sputtering method wasused to prepare multilayer. Silicon coated with an oxide film having athickness of approximately 1,000 A was used as a substrate.

Cu and Fe₀.1 Co₀.9 alloy targets were alternately sputtered fifteentimes to stack fifteen unit layers each comprising a nonmagnetic Culayer having a thickness of 9 A and a magnetic Fe₀.1 Co₀.9 alloy layerhaving a thickness of 15 A (the number of the unit layer is 15), therebyforming the multilayer, as shown in FIG. 1. A condition of filmformation was identical with that of Example 1. The multilayer isreferred to (Fe₀.1 Co₀.9 15A/Cu9A)₁₅.

Then, the magnetoresistance effect of the prepared multilayer wasmeasured by means of the conventional four point method. FIG. 6, whichappears similar to FIG. 4, illustrates the result of the measurement.The magnetoresistance ratio ΔR/R was determined from the graph to showthe magnetoresistance effect of the element. It was 8.15%, or asatisfactorily large value. It was confirmed that the multilayer whichused a Fe₀.1 Co₀.9 alloy for the magnetic layers and Cu for thenonmagnetic layers was suitable for a magnetoresistance effect element.

EXAMPLE 4

In this example, magnetic layers were made of a Fe₀.75 Co₀.25 alloynonmagnetic layers were made of Cr. The ion beam sputtering method wasused to prepare multilayer. MgO (100) single crystal was used as asubstrate.

Cr and Fe₀.75 Co₀.25 alloy targets were alternately sputtered fifteentimes to stack fifteen unit layers each comprising a nonmagnetic Crlayer having a thickness of 13 A and a magnetic Fe₀.75 Co₀.25 alloylayer having a thickness of 20 A (the number of the unit layer is 15),thereby forming the multilayer, as shown in FIG. 1. A condition of filmformation was identical with that of Example 1. The multilayer isreferred to (Fe₀.75 Co₀.25 20A/Cr13A)₁₅.

Then, the magnetoresistance effect of the prepared multilayer wasmeasured by means of the conventional four point method. FIG. 7, whichappears similar to FIG. 4, illustrates the result of the measurement.The magnetoresistance ratio ΔR/R was determined from the graph to showthe magnetoresistance effect of the element. It was 6.8%, or asatisfactorily large value. It was confirmed that the multilayer of thisexample was suitable for a magnetoresistance effect element.

EXAMPLE 5

In this example, magnetic layers were made of a Ni₀.4 (Fe₀.5 Co₀.5)₀.6alloy and nonmagnetic layers were made of Cu. The ion beam sputteringmethod was used to prepare multilayer. Silicon coated with a oxide filmhaving a thickness of approximately 1,000 A was used as a substrate.

Cu and Ni₀.4 (Fe₀.5 Co₀.5)₀.6 alloy targets were alternately sputteredfifteen time to stack fifteen unit layers each comprising a nonmagneticCu layer having a thickness of 9 A and a magnetic Ni₀.4 (Fe₀.5 Co₀.5)₀.6alloy layer having a thickness of 15 A (the number of the unit layer is15), thereby forming the multilayer, as shown in FIG. 1. A condition offilm formation was identical with that of Example 1. The multilayer isreferred to (Ni₀.4 (Fe0.5Co₀.5)₀.6 15A/Cu9 A)₁₅.

Then, the magnetoresistance effect of the prepared multilayer wasmeasured by means of the conventional four points method. FIG. 8, whichappears similar to FIG. 4, illustrates the result of the measurement.The magnetoresistance ratio ΔR/R was determined from the graph to showthe magnetoresistance effect of the element. It was 7.8%, or asatisfactorily large value. It was confirmed that the multilayer of thisexample was suitable for a magnetoresistance effect element.

EXAMPLE 6

In this example, magnetic layers were made of a Ni₀.25 (Fe₀.75Co₀.25)₀.75 alloy and nonmagnetic layers were made of Cr. The ion beamsputtering method was used to prepare multilayer. MgO (100) singlecrystal was used as a substrate.

Cr and Ni₀.25 (Fe₀.75 Co₀.25)₀.75 alloy targets were alternatelysputtered fifteen times to stack fifteen unit layers each comprising anonmagnetic Cr layer having a thickness of 13 A and a magnetic Ni₀.25(Fe₀.75 Co₀.25)₀.75 alloy layer having a thickness of 20 A (the numberof the unit layer is 15), thereby forming the multilayer, as shown inFIG. 1. A condition of film formation was identical with that ofExample 1. The multilayer is referred to (Ni₀.25 (Fe₀.75 Co₀.25)₀.7520A/Cu13A)₁₅.

Then, the magnetoresistance effect of the prepared multilayer wasmeasured by means of the conventional four points method. FIG. 9, whichappears similar to FIG. 4, illustrates the result of the measurement.The magnetoresistance ratio ΔR/R was determined from the graph to showthe magnetoresistance effect of the element. It was 5.7%, or asatisfactorily large value. It was confirmed that this multilayer wassuitable for a magnetoresistive effect element.

COMPARATIVE EXAMPLE 1

In this comparison example, magnetic layers were made of Co andnonmagnetic layers made of Cu. The ion beam sputtering method was usedto prepare multilayer. Quartz was used as substrate.

Firstly, an Fe buffer layer having a thickness of 50 A was formed on thequartz substrate. Subsequently, Cu and Co targets were alternatelysputtered fifteen times to stack fifteen unit layers each comprising anonmagnetic Cu layer having a thickness of 9 A and a Co layer having athickness of 7 A (the number of the unit layer is 15), thereby formingmultilayer, as shown in FIG. 1. A condition of film formation wasidentical with that of Example 1. The multilayer is referred to(Co7A/Cu9A)₁₅.

Then, the magnetoresistance effect of the prepared multilayer wasmeasured by means of the conventional four points method. FIG. 10, whichappears similar to FIG. 4, illustrates the result of the measurement.The magnetoresistance ratio ΔR/R was determined from the graph to showthe magnetoresistance effect of the element. It was 4.4%, or aconsiderably low value as compared to those of the above examples.

COMPARATIVE EXAMPLE 2

In this comparison example, magnetic layers were made of Fe andnonmagnetic layers made of Cr. The ion beam sputtering method was usedto prepare multilayer. A MgO (100) single crystal was used as asubstrate.

Cr and Fe targets were alternately sputtered fifteen times to stackfifteen unit layers each comprising a nonmagnetic Cr layer having athickness of 13 A and an Fe layer having a thickness of 20 A (the numberof the unit layer is 15), thereby forming the multilayer, as shown inFIG. 1. A condition of film formation was identical with that ofExample 1. The multilayer is referred to (Fe20A/Cr13A)₅.

Then, the magnetoresistance effect of the prepared multilayer wasmeasured by means of the conventional four points method. FIG. 11, whichappears similar to FIG. 4, illustrates the result of the measurement.The magnetoresistance ratio ΔR/R was determined from the graph to showthe magnetoresistance effect of the element. It was 2.4%, or aconsiderably low value as compared to those of the above examples.

EXAMPLE 7

In this example, the magnetic layers were made of a Fe₀.1 Co₀.9 alloynonmagnetic layers were made of Cu. The ion beam sputtering method wasused to prepare multilayer. The condition under which the multilayer wasprepared was different from that of Example 1.

The inventors of the present invention found that the magnetoresistanceratio of the multilayer is very sensitive to the accelerating voltage atthe time of film formation. Therefor, the operation of film formationwas conducted for this example with the accelerating voltage raised to600 V and the beam current maintained to 30 mA. The attained vacuumlevel and the Ar partial pressure were same as those of Example 1.

Firstly, a magnetic Fe₀.1 Co₀.9 layer was formed on a substrate of MgO(110) single crystal to the thickness of 10 A and a nonmagnetic Cu layerwas formed thereon to the thickness of 10 A to produce an unit layer.Then, other fifteen unit layers, which were identical with the firstone, were sequentially formed on the first unit layer to produce themultilayer having a total of sixteen unit layers. The multilayer isreferred to (Fe₀.1 Co₀.9 10A/Cu10A)₁₆.

For the purpose of comparison, similar multilayer comprising sixteenunit layers, each consisting of a magnetic layer and a nonmagneticlayer, was prepared in the same way except that the magnetic layers weremade of Co. This multilayer is referred to (Co10 A/Cu10 A)₁₆.

Then, the magnetoresistance effect of each of the prepared multilayerwas measured by means of the conventional four points method todetermine the magnetoresistance ratio ΔR/R of the multilayer. It was39.4% for (Fe₀.1 Co₀.9 10A/Cu10A)₁₆ and 31.5% for (Co10A/Cu10A)₁₆. Thus,it was confirmed that (Fe₀.1 Co₀.9 10 A/Cu10A)₁₆ comprising magneticlayers made of an alloy had a higher magnetoresistance ratio.

EXAMPLE 8

In this example, the magnetic layers were made of a Fe₀.1 Co₀.9 alloynonmagnetic layers were made of a CuAu alloy. The ion beam sputteringmethod was used to prepare multilayer.

In the preparation of the multilayer under a condition which asidentical with that of Example 7, firstly an Fe buffer layer was formedon a quartz substrate to a thickness of 50 A. Then, a nonmagnetic CuAulayer was formed thereon to a thickness of 10 A and a magnetic Fe₀.1Co₀.9 layer was formed further on the nonmagnetic CuAu layer to athickness of 20 A to produce an unit layer. Fifteen more unit layerswere sequentially formed on the first unit layer to produce themultilayer having a total of sixteen unit layers. The multilayer isreferred to (Fe₀.1 Co₀.9 20 A/CuAu10 A)₁₆.

For comparison, similar multilayer comprising sixteen unit layers, eachconsisting of a magnetic layer and a nonmagnetic layer, was prepared inthe same way except that the magnetic layers were made of Co. Thismultilayer is referred to (Co20A/CuAu10A)₁₆.

Then, the magnetoresistance effect of each of the prepared multilayerwas measured by means of the conventional four points method todetermine the magnetoresistance ratio ΔR/R of the multilayer. It was20.2% for (Fe₀.1 Co₀.9 20A/CuAu10A)₁₆ and 17.8% for (Co20A/CuAu10A)₁₆.Thus, it was confirmed that (Fe₀.1 Co₀.9 20A/CuAu10A)₁₆ comprisingmagnetic layers made of an alloy had a higher magnetoresistance ratio.

EXAMPLE 9

In this example, the magnetic layers were made of a Fe₀.1 Co₀.9 alloyand nonmagnetic layers were made of Au. The ion beam sputtering methodwas used to prepare multilayer.

In the preparation of the multilayer under a condition which asidentical with that of Example 7, firstly an Fe buffer layer was formedon a quartz substrate to a thickness of 50 A. Then, a nonmagnetic Aulayer was formed thereon to a thickness of 10 A and a magnetic Fe₀.1Co₀.9 layer was formed on the nonmagnetic Au layer to a thickness of 20A to produce a unit layer. Fifteen more unit layers were sequentiallyformed on the first unit layer to produce the multilayer having a totalof sixteen unit layers. The multilayer is referred to (Fe₀.1 Co₀.920A/Au10A)₁₆.

For comparison, similar multilayer comprising sixteen unit layers, eachconsisting of a magnetic layer and a nonmagnetic layer, were prepared inthe same way except that the magnetic layers were made of Co. Thismultilayer is referred to (Co20A/Au10A)₁₆.

Then, the magnetoresistance effect of each of the prepared multilayerwas measured by means of the conventional four points method todetermine the magnetoresistance ratio ΔR/R of the multilayer. It was15.3% for (Fe₀.1 Co₀.9 20A/Au10A)₁₆ and 10.8% for (Co20A/Au10A)₁₆. Thus,it was confirmed that (Fe₀.1 Co₀.9 20A/CuAu10A)₁₆ comprising magneticlayers made of an alloy had a higher magnetoresistance ratio.

EXAMPLE 10

In this example, the magnetic layers were made of a Ni₀.5 Fe₀.2 alloyand nonmagnetic layers were made of Cu. The ion beam sputtering methodwas used to prepare multilayer.

In the preparation of multilayer under a condition which as identicalwith that of Example 7, firstly an Fe buffer layer was formed on aquartz substrate to the thickness of 50 A. Then, a nonmagnetic Cu layerwas formed thereon to a thickness of 10 A and a magnetic Ni₀.8 Fe₀.2layer was formed on the nonmagnetic Cu layer also to the thickness of 10A to produce an unit layer. Fifteen more unit layers were sequentiallyformed on the first unit layer to produce the multilayer having a totalof sixteen unit layers. The multilayer is referred to Ni₀.8 Fe₀.210A/Cu10A)₁₆.

For comparison, similar multilayer comprising sixteen unit layers, eachconsisting of a magnetic layer and a nonmagnetic layer, were prepared inthe same way except that the magnetic layers were made of Ni. Thismultilayer is referred to (Ni10A/Cu10A)₁₆.

Then, the magnetoresistance effect of each of the prepared multilayerwas measured by means of the convention four points method to determinethe magnetoresistance ratio ΔR/R of the multilayer. It was 18.3% for(Ni₀.8 Fe₀.2 10 A/Cu10 A)₁₆ and 10.1% for (Ni10 A/Cu10 A)₁₆. Thus, itwas confirmed that (Ni₀.8 Fe₀.2 10A/Cu10A)₁₆ comprising magnetic layersmade of an alloy had a higher magnetoresistance ratio.

EXAMPLE 11

In this example, magnetic layers were made of a Ni₀.8 Fe₀.2 alloy andnonmagnetic layers were made of Au. The ion beam sputtering method wasused to prepare multilayer.

In the preparation of the multilayer under a condition which asidentical with that of Example 7, firstly an Fe buffer layer was formedon a quartz substrate to a thickness of 50 A. Then, a nonmagnetic Aulayer was formed thereon to a thickness of 10 A and a magnetic Ni₀.8Fe₀.2 layer was formed on the nonmagnetic Au layer to a thickness of 20A to produce a unit layer. Fifteen more unit layers were sequentiallyformed on the first unit layer to produce the multilayer having a totalof sixteen unit layers. The laminate is referred to Ni₀.8 Fe₀.220A/Au10A)₁₆.

For comparison, similar multilayer comprising sixteen unit layers, eachconsisting of a magnetic layer and a nonmagnetic layer, was prepared inthe same way except that the magnetic layers were made of Ni. Thismultilayer is referred to (Ni20A/Au10A)₁₆

Then, the magnetoresistance effect of each of the prepared multilayerwas measured by means of the conventional four points method todetermine the magnetoresistance ratio ΔR/R of the multilayer. It was13.4% for (Ni₀.8 Fe₀.2 20A/Au10A)₁₆ and 8.2% for (Ni20A/Au10A)₁₆. Thus,it was confirmed that (Ni₀.8 Fe₀.2 20 A/Au10 A)₁₆ comprising magneticlayers made of an alloy had a higher magnetoresistance ratio.

EXAMPLE 12

In this example, magnetic layers were made of Permalloy of Ni₀.8 Fe₀.2and nonmagnetic layers were made of Cu. The ion beam sputtering methodwas used to prepare multilayer.

A MgO (110) single crystal substrate was placed in a chamber and theinside of the chamber was evacuated to 5×10⁻⁷ Torr. Then, Ar gas wasintroduced into the chamber to raise the pressure to 1×10⁻⁴ Torr and asputtering operation was carried out, using an accelerating voltage of700 V and a beam current of 30 mA. Two different types of targets madeof a Ni₀.8 Fe₀.2 alloy and Cu were used. Firstly, a magnetic Ni₀.8 Fe₀.2layer was formed on the MgO (110) substrate and then a nonmagneticcopper (Cu) layer was formed thereon to produce a unit layer.Thereafter, fifteen more unit layers were sequentially formed on thefirst unit layer to produce the multilayer comprising a total of sixteenunit layers.

FIG. 12 shows a torque curve of the multilayer. Since the torque curveis twofold symmetry as shown in FIG. 12, it was confirmed that themagnetic layers have in-plane uniaxial magnetic anisotropy.

FIG. 13 is a graph showing the magnetoresistance effect of the elementalong the direction of the axis of easy magnetization of the magneticlayers. It was confirmed that the saturated magnetic field H_(S) of theelement was as low as 1.2 kOe, while its magnetoresistance ratio was ashigh as 16.7%, as shown in FIG. 13.

When the multilayer having the same structure of above-describedmultilayer was formed on a SiO2 substrate, it was found that no uniaxialmagnetic anisotropy was obtained and its magnetoresistance ratio was5.5%.

As shown in FIG. 13, the resistance of the element began to changearound 1.0 kOe and rapidly saturated with a small change ofapproximately 200 e in the magnetic field, making the graph rise andfall very sharply. It may be apparent that a highly sensitive magneticfield sensor can be realized by utilizing these sharply rising andfalling areas.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices, shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A magnetoresistance effect element comprisingmultilayer formed by stacking magnetic and non-magnetic layers in amanner to produce a magnetoresistance effect, said magnetic layerscontaining an alloy represented by Fe_(1-x) Co_(x) where 0.5≦x<1 andhaving a thickness of 2 to 50 Å, and said non-magnetic layers containingCu or an alloy containing Cu, and having a thickness of 2 to 100 Å, anytwo magnetic layers adjacent to each other with one of said non-magneticlayers interposed therebetween being antiferromagnetically coupled undera condition that a magnetic field is not substantially applied thereto.2. A magnetoresistance effect element comprising multilayer formed bystacking magnetic and non-magnetic layers in a manner to produce amagnetoresistance effect, said magnetic layers containing an alloyrepresented by Ni_(1-y) (Fe_(1-x) Co_(x))_(y) where 0.5≦x≦1 and 0<y<1having a thickness of 2 to 50 Å, and said non-magnetic layers containingCu or an alloy containing Cu, and having a thickness of 2 to 100 Å, anytwo magnetic layers adjacent to each other with one of said non-magneticlayers interposed therebetween being antiferromagnetically coupled undera condition that a magnetic field is not substantially applied thereto.3. A magnetoresistance effect element, comprising multilayer formed bystacking magnetic and non-magnetic layers in a manner to produce amagnetoresistance effect, said magnetic layers containing an alloyrepresented by Fe_(1-x) Co_(x), where 0.5≦X<1 and having a thickness of2 to 50 Å, and said non-magnetic layers containing Cu or an alloycontaining Cu and having a thickness of 2 to 100 Å, any two magneticlayers adjacent to each other with one of said non-magnetic layersinterposed therebetween being antiferromagnetically coupled.
 4. Amagnetoresistance effect element according to claim 2, wherein saidmagnetic layers contain an alloy represented by Ni_(1-y) (Fe_(1-x)Co_(x))_(y), where 0.5≦x≦1 and 0<y<1, and said nonmagnetic layerscontain Cu.
 5. A magnetoresistance effect element according to claim 2,wherein said magnetic layers contain an alloy represented by Ni_(1-y)(Fe_(1-x) Co_(x))_(y) where 0.5≦x≦0.9 and 0.7≦y<1, and said nonmagneticlayers further contain chromium.
 6. A magnetoresistance effect elementaccording to claim 3, wherein said magnetic layers contain an alloyselected from the group consisting of an Fe--Co alloy and an Fe--Ni--Coalloy.
 7. A magnetoresistance effect element according to claim 3,wherein said magnetic layers contain an alloy represented by Fe_(1-x)Co_(x), where 0.5≦x<1, and said nonmagnetic layers contain Cu.
 8. Amagnetoresistance effect element according to claim 3, furthercomprising a substrate for supporting said multilayer.
 9. Amagnetoresistance effect element according to claim 9, furthercomprising a buffer layer formed of a soft magnetic material andarranged between said substrate and said multilayer.
 10. Amagnetoresistance effect element according to claim 3, wherein saidmagnetic layers have a thickness of 7 to 50 Angstrom.
 11. Amagnetoresistance effect element according to claim 3, wherein saidnonmagnetic layers have a thickness of 9 to 100 Angstrom.
 12. Amagnetoresistance effect element according to claim 8, wherein saidsubstrate is made of a member selected from the group consisting ofSiO₂, MgO and Si.
 13. A magnetoresistance element of claim 3, whereinsaid magnetic layers comprise ferromagnetic elements, said ferromagneticelements selected from the group consisting of Fe and Co.